I had four MT4 platforms on my computer using an earlier version. All of these platforms were updated to 610 without warning.
Unfortunately, my broker, MBTrading doesn't support any platform greater than 509. I need to know how I can go back to
version 509. I deleted everything and re-installed 509, but the file structure remains 610. PLEASE HELP!!!

caljac54: I had four MT4 platforms on my computer using an earlier version. All of these platforms were updated to 610 without warning.
Unfortunately, my broker, MBTrading doesn't support any platform greater than 509. I need to know how I can go back to
version 509. I deleted everything and re-installed 509, but the file structure remains 610. PLEASE HELP!!!

caljac54:
I had four MT4 platforms on my computer using an earlier version. All of these platforms were updated to 610 without warning.
Unfortunately, my broker, MBTrading doesn't support any platform greater than 509.

Without warning? https://forum.mql4.com/56885/ warned of it SEVEN months in advance ( 2013.07.24 16:43 .) The banner image (at the top of the page) warned of it more than a month in advance. If your broker didn't warn you, who's fault is that.

The update is pushed from your broker, not from MQ. If your broker doesn't support 6xx, why did they upgrade you? Why aren't they supporting 6xx?

I had four MT4 platforms on my computer using an earlier version. All of these platforms were updated to 610 without warning.
Unfortunately, my broker, MBTrading doesn't support any platform greater than 509. I need to know how I can go back to
version 509. I deleted everything and re-installed 509, but the file structure remains 610. PLEASE HELP!!!

This is a problem/bug with the update system. If one broker triggers the update, then all your MT4 installations will use it. You can revert your MBTrading platform by simply restoring the Program Files folder from a recent backup. Then search your system for hidden MetaQuotes/WebInstall/ folders and delete them.

Keep an eye on the Journal tabs of your terminals for something like this:

14:07:57 LiveUpdate: finished
14:07:21 LiveUpdate: new version 4.00 build 610 is available

That is all the warning you may get of an impending update. It's time to make sure you have a good backup before you next start any of your terminals!